refactor(snapshot): remove element detection

[msmps]

Summary

• delete heuristic UI element classification, segmentation, style-grid adapters, tests, and direct dependency
• reduce snapshots to terminal size, cursor state, optional text, and optional content hash
• remove the unused snapshot ID counter from live and finalized capture paths
• update CLI help, documentation, npm guidance, and the bundled skill around text-first navigation
• introduce protocol v3 for the breaking snapshot request/response contract while retaining existing minimum versions for output and status

Breaking changes

Full JSON snapshots no longer contain elements or snapshot_id. Snapshot requests now require protocol v3, so mismatched client/daemon binaries receive the existing actionable upgrade guidance instead of attempting to decode incompatible evidence.

Verification

• cargo fmt --all
• cargo test --workspace (188 passed)
• cargo clippy --all --benches --tests --examples --all-features
• ./scripts/version-sync.sh --check
• bash -n skills/pilotty/templates/dialog-interaction.sh skills/pilotty/templates/multi-session.sh skills/pilotty/templates/vim-workflow.sh
• git diff --check